NDT Inspection of Critical ABC Details to Assure Life Cycle Performance and Avoid Future Unforeseen Excessive Repairs

摘要

Accelerated bridge construction (ABC) employs prefabricated bridge elements moved to the bridge location and installed in place. Accordingly, ABC reduces many uncertainties associated with construction processes and performance during service life. It also improves the life cycle cost by reducing construction time and traffic interruptions, better control over schedule, and normally by the higher quality of elements resulting in better life-cycle performance. Nevertheless, prefabricated elements need to be made continuous using cast-in-place joints. ABC "closure joints" connecting deck elements to each other and to the bridge girders have greater exposure to degrading environmental effects, and often there is more focus on their evaluation. These joints, expected to become serviceable quickly can therefore be viewed as critical elements of the ABC bridges. Instances of defective (leaky) joints have been reported, and concerns have been raised about the long-term durability of the joints. The long-term deflections and environmental loading will only exacerbate this situation. These may overshadow the many advantages of ABC specifically as life-cycle performance and costs are concerned. Hence, health monitoring of ABC critical details, i.e., joints, becomes a priority for first assuring a life-cycle performance compatible with the prefabricated elements, and more importantly to address potential problems before damages become excessive. A variety of non-destructive testing (NDT) methods has been utilized in the past for structural health monitoring of bridges in general. However, a concerted attempt for evaluation of NDT techniques, comparison of capabilities, and selection of methods most applicable to ABC closure joints is lacking. As a part of the ABC-UTC program at the Florida International University, a research study is being undertaken to identify the defects associated with closure joints, to evaluate NDT methods for applicability to ABC closure joints, and finally to determine the most promising methods. This paper summarizes the results of this research study.